fix(spanner): end spans for read-write methods

Author: harshachinta

google-cloud-spanner/src/main/java/com/google/cloud/spanner/DatabaseClientImpl.java

@@ -282,6 +282,8 @@ public TransactionRunner readWriteTransaction(TransactionOption... options) {
       span.setStatus(e);
       span.end();
       throw e;
+    } finally {
+      span.end();
     }
   }
 
@@ -294,6 +296,8 @@ public TransactionManager transactionManager(TransactionOption... options) {
       span.setStatus(e);
       span.end();
       throw e;
+    } finally {
+      span.end();
     }
   }
 
@@ -306,6 +310,8 @@ public AsyncRunner runAsync(TransactionOption... options) {
       span.setStatus(e);
       span.end();
       throw e;
+    } finally {
+      span.end();
     }
   }
 
@@ -318,6 +324,8 @@ public AsyncTransactionManager transactionManagerAsync(TransactionOption... opti
       span.setStatus(e);
       span.end();
       throw e;
+    } finally {
+      span.end();
     }
   }